Stabilized photographic silver halide emulsions containing iodine complexes of poly-n-vinyl-2-oxazolidinones



3,060,028 STABHJZED PHOTOGRAPHIC SILVER HALIDE EMULSIONS CONTAININGIUDINE (30M- PLEXES F POLY-N-VINYL 2 OXAZOLIDI- NONES Fritz Dersch,Binghamton, N.Y., assignor to General Aniline & Film Corporation, NewYork, N.Y., a corporation of Delaware N0 Drawing. Filed Jan. 19, 1961,Ser. No. 83,647 6 Claims. (Cl. 96-66) This invention relates to lightsensitive silver halide photographic emulsions stabilized with iodinecomplexes of poly-N-vinyl-Z-oxazolidinones and to methods of preparingsuch stabilized emulsions.

It is known that silver halide photographicemulsions, when stored forany length of time, becomes spontaneously developable without exposureto light. Consequently, when photographic elements containingexcessively aged emulsion are exposed and developed, there is formed,even in the unexposed areas of the plate, a certain amount of developedsilver. Optical opacity produced in the unexposed areas is commonlyreferred to as fog, and emulsions which give rise to this condition aredesignated as fogged emulsions.

The phenomenon of fog in photographic emulsions has engaged theattention of photographic chemists for many years. It has been studiedin great detail and numerous reasons have been put forth to account forits occurrence. For instance, emulsions stored under conditions of highhumidity tend to grow foggy. In fact, it is a common practice to testphotographic emulsions by subjecting them to excessive humidity and/ortemperature. Such information, of course, is very important, since manyemulsions may encounter the aforedescribed conditions in tropicalclimates. Photographic fog also can be produced by exposure tochemicals, such as hydrogen, sulfide, or other reactive sulfurcompounds, including strongly reducing materials, some of which mayoccur in the atmosphere.

A large number of substances known to the art an antifoggants and/orstabilizers have been described in the literature as being eifective inretarding fog when such entities are incorporated in light sensitivesilver halide emulsions. In this connection, reference is made to themercapto derivatives of benzothiazole, benzimidazole and other relatedazoles. Although these compounds have been found eifective for reducingor retarding fog buildup, there is produced a secondary efiect whichmanifests itself in a generally lowering of sensitivity and speed of theemulsion and in some instances may even reduce its optical or dyesensitization.

It has now been discovered that photographic light sensitive silverhalide emulsions, which have been stabilized with certainpoly-N-vinyl-Z-oxazolidinones in the form of their iodine complexes,remain remarkably free of any tendency toward fog build-up on storage,and yet emulsions stabilized in this manner maintain their overallphotographic sensitivity. The provision of silver halide photographicemulsion stabilized or protected by the action of iodine complexes ofpoly-N-vinyl-Z-oxazolidinones constitute the purposes and objects ofthis invention.

The poly-N-vinyl-Z-oxazolidinone iodine complexes which I havediscovered to be excellent antifoggant agents for silver halideemulsions are known entities and are de scribed in the chemicalliterature; Chem. and Engr. News, September 5, 1960 (pp. 56-57). Suchcompounds 3,h0,028 Patented Oct. 23, 1962 can be formulisticallyillustrated by the following type of general formula:

wherein n is a whole integer, the value of which is sufficient toproduce a polymer having an average molecular weight of about 150,000,and R is selected from the class consisting of hydrogen and lower alkylgroups.

I have ascertained that the iodine complex of poly-N-vinyl-5-methyl-2-oxazolidinone having an average molecular weight ofabout 150,000 has excellent antifoggant properties for greatly retardingfog in silver halide emulsions. This particular poly-2-oxazolidinone waspurchased on the open market under the trade name Devlex, and is soldunder this name by the Dow Chemical Company. As the iodine complex,poly-N-vinyl-5-methyl- -oxazolidinone contains 5.1% free iodine, whichis bound to the polymer molecule analogously to iodine in the familiarstarch iodine complex.

The aforementioned compounds can be utilized in various ways in order tosecure beneficial efiects and fog reduction. For instance, thecomponents can be incorporated in the silver halide emulsions asripening finals or as coating finals. Ripening finals are added duringthe ripening or the sensitivity increasing stage of the emulsion makingprocess. These additions may be made before, during or after the doubledecomposition reaction between the soluble silver salt such as silvernitrate and the soluble halide, such as potassium bromide in thepresence of a colloid carrier. By colloid carrier is intended the mediumin which is contained the light sensitive silver halide salts. Typicalexamples of such carriers include gelatin, PVA, solubilized casein,carboxymethyl cellulose, albumin and the like.

Coating finals are customarily added to the emulsion just prior tocoating on a suitable support such as glass, paper, or film, at a timewhen the emulsion is approaching its maximum sensitivity.

When used as a ripening final the poly-N-vinyl-Z- oxazolidinone-iodinecomplex is preferably used in a concentration ranging from 1 tomilligrams per 0.4 mole of silver halide, and, when used as coatingfinals is employed in a ratio varying from 10 to 300 milligrams per 0.4mole of silver halide. The concentration will vary with the varioustypes of emulsion which is used and it is advisable to determine theoptimum concentration from case to case. In some instances, it isdesirable to apply this group of antifoggants and stabilizers inadjacent layers, e.g., in a separate undercoating layer or in theanti-abrasion gelation surface. In other cases, it may be desirable toutilize them in one or all of the processing baths or in preandpostbaths.

The antifoggants as described herein can be advantageously employed inconnection with any type of photographic emulsion, e.g., non-sensitized,orthochromatic, panchromatic, X-ray emulsions, paper emulsions, coloremulsions or the like. It has also been ascertained that the compoundsof the invention are capable of use in combination with other knownantifoggants and stabilizers, as well as other photographic adjunctssuch as reduction and metal and noble metal sensitizers and incombination with a hydroxy polyphenoxy derivative of the type obtainedby reacting ethylene oxide with alcohol phenol amine or the like asdescribed in U.S.P. 1,970,578.

The invention is illustrated by the following examples, but it is to beunderstood that the invention is not to be restricted thereto.

Example I A silver halide emulsion in gelatin containing 4% silveriodide and 96% silver bromide was prepared in a conventional manner andbrought up to its maximum light sensitivity and then readied forcoating. Finals were added such as sensitizing dyes, stabilizers andhardening agents. A 1.0% (by Weight) solution of the iodine complex(5.1% free iodine) of Devlex l30-previously described herein-in waterwas prepared and added to the emulsion as an antifoggant and stabilizer.The emulsion samples contained about 0.4 mole of silver halide. Theso-prepared emulsion samples were coated on a suitable cellulose esterbase and dried. Samples of these film coatings were exposed in a Type113 sensitometer and developed in a developer of the followingcomposition:

Grams Metol 1.5 Sodium sulfite, anhydrous 45.0 Sodium bisulfi 1.0Hydroquinone 3.0 Sodium carbonate, monohydrated 6.0 Potassium bromide0.80 Water to make 1.0 liter Quantity of Compound Relative Fog at OvenOven Fog Added Speed 14 Dev. Speed at 7 Dev.

Beneficial effects in fog reduction may be obtained when solutions ofpolyvinyloxazolidinone iodine are incorporated in the silver halideemulsions as ripening finals or as coating finals. Ripening finals areadded during the ripening or the sensitivity increasing stage of theemulsion making process. Such additions may be made before, during orafter the addition of the soluble silver salt to the soluble halides inpresence of a suitable colloid, such as gelatin, PVA, solubilized caseinor albumin. Coating finals are added to the emulsion just prior tocoating it on a suitable support (glass, paper, film) when the emulsionhas nearly obtained its maximum sensitivity.

When used as ripening finals, polyvinyloxazolidinone iodine is best usedin a concentration of l to 100 milligrams per 0.4 mole of silver halideand when used as coating final in a concentration of ten to 300milligrams per 0.4 mole of silver halide. The concentration used dependsvery much on the type of emulsion which is used, and it is advisable todetermine the optimum concentration from case to case. In some cases itis advantageous to apply PVC-iodine in adjacent layers, e.g., in aseparate undercoating layer or in the antiabrasion gelatin surface. Inother cases, it is desirable to apply them in one or all processingbaths or in preand postbaths. PVC-iodine may be used in various kinds ofphotographic emulsions, e.g., non-sensitized, orthochromatic,panchromatic, X-ray emulsions, paper emulsions, color emulsions.

PVC-iodine may be used in combination with other known anti-foggants andstabilizers, also in combination with sulfur, reduction and metal, andnoble metal sensitizers also in combination with polyoxyalkylenes, theirderivatives and other accelerators such as polyvinylpyrrolidone (PVP) orpoly-N-vinyl-2-oxazolidinone.

The iodine complex of a poly-N-vinyl-2-oxazolidinone is prepared bymixing a solution of the oxazolidinone polymer in a solvent thereforsuch as methanol, ethanol, or methylene chloride with a solution ofiodine in a similar solvent. If desired, an aqueous solution ofpolyvinyl oxazolidinone may be combined with an aqueous solution ofiodine such as Lugol solution followed by mixing. The resulting mixedsolutions, which now contain the polyvinyloxazolidinone iodine complex,may be used directly if desired or the solutions may be reduced to a drypowder for subsequent redissolution in water. Lugol solution is known tothe art and commonly comprises a solution containing 5 grams of iodineand 10 grams (U.S.P.) or 7.5 grams (B.P.C.) of potassium iodine per cc.of solvent; Hackhs Chemical Dictionary, Third Edition.

Example II The procedure of Example I was followed in this caseexcepting that the Devlex iodine complex was replaced bypoly-N-vinyl-Z-oxazolidinone iodine complex having a molecular weight ofapproximately 150,000. The results were similar to those obtained inExample I.

I claim:

1. A light sensitive photographic material comprising a base and a lightsensitive silver halide emulsion layer, said light sensitive materialcontaining as an antifoggant the iodine complex of a compoundrepresented by the following formula:

RGH--O N -dH-GH- 11 wherein n is an integer the value of which issufiiciently high to produce an average molecular weight of about150,000 and R is selected from the class consisting of hydrogen andlower alkyl.

2. The composition as defined in claim 1 wherein the said anti-foggantis located in the silver halide emulsion.

3. The article as defined in claim 1 wherein said antifoggant is locatedin the layer adjacent to said silver emulsion.

4. A light sensitive photographic material comprising a base with alight sensitive silver halide emulsion thereon, said emulsion containingas an antifoggant, the iodine complex of a compound represented by thefollowing formula:

H3CCHGO H: N -(EH-CHz- 11 wherein n is a positive integer the value ofwhich is sufficient to produce an average molecular weight of about150,000.

5. The process of minimizing and preventing fog in light sensitivesilver halide materials, comprising a base having a light sensitivesilver halide emulsion thereon which comprises exposing said emulsion toa light image and developing said emulsion in the presence of the iodinecomplex of an antifoggant compound represented by the following generalformula:

-dH-GH= 11 wherein n is an integer the value of which is sufficientlyhigh to produce molecular weight of about 150,000 and R is selected fromthe class consisting of hydrogen and lower alkyl.

6. The process as defined in claim 5 wherein the antifoggant isrepresented by the following formula:

HsCCH-(JO JH-CHz n where n is an integer the value of which issufliciently high to produce molecular weight of about 150,000.

No references cited.

5. THE PROCESS OF MINIMIZING AND PREVENTING FOR IN LIGHT SENSITIVESILVER HALIDE MATERIALS, COMPRISING A BASE HAVING A LIGHT SENSTIVESILVER HALIDE EMULSION THEREON WHICH COMPRISES EXPOSING SAID EMULSION TOA LIGHT IMAGE AND DEVELOPING SAID EMULSION IN THE PRESENCE OF THE IODINECOMPLEX OF AN ANTIFOGGANT COMPOUND REPRESENTED BY THE FOLLOWING GENERALFORMULA: